Something like pulled pork or Bo Ssam or porchetta could be fun? Sort of evocative of the whole roast pig but scaled down. Maybe serve with those little Hawaiian bread rolls so guests can make sandwiches? I'm a big fan of little cocktail meatballs, too - they're pretty much always a hit, and so easy to make ahead, in bulk, and keep warm in a crock pot.

Are your friends the type to enjoy seaweed salad (japanese style) and poke (marinated raw fish or octopus)? Because that is pretty much all I eat when I am in Hawaii. The poke from from grocery stores is so good! You could serve a teaspoon of poke in a wanton crisp as an appetizer. There are many great favors - I like kimchi ahi poke. Of course, this requires being careful of food prep and temp before serving.

Try kalua pork... that's usually an all-around hit. Might be easier for you if you do it in the crock pot, depending on how many people you're doing this for. Put it on slider buns, or (better yet) Hawaiian bread cut to make slider-type buns.

If you want to serve "local kine" food, as in what type of "heavy pupu" may be served at a local Hawaiian style party, might I suggest kalbi ribs, limu poke, kalua pork, miso butterfish, any kine laulau, haupia, chicken adobo, pancit, Spam musubi, sushi, manapua, and huli huli chicken. I lived in Hawaii for 15 years and that is what I had at every party in had in my garage/lanai. Along with plenty of beer (add ice to keep it cold!). Shave ice never hurts either. Serve with azuki bean paste and add matcha to the water for green tea flavor. No ka oi!